Art of cracking hydrocarbons



May 29, 1934- E. w. ISOM ET AL 1,960,908

ART OF CRACKING HYDROCARBONS Filed June 12, 1929 d1 6 1 A/e/ 0/7ATTORNEYS Patented May 29, 1934 UNITED STATES PATENT OFFICE ART OFCRACKING HYDROCARBONS tion of Maine Application June 12, 1929, SerialNo. 370,281

2 Claims.

This invention relates to improvements in the manufacture of lowerboiling hydrocarbon oils, such as gasoline, from higher boilinghydrocarbon oils, such as gas oil, crude oil and reduced crude oil.

The present invention provides an improved method of cracking higherboiling hydrocarbon oils in which high boiling oil is heated to a highcracking temperature, upwards of about 900 F.,

under superatmospheric pressure to produce a high yield of gasoline in asingle passage as a stream of high velocity through a heating operation, in which the hot oil products from the heat ing operation aresuddenly cooled by direct heat exchange with introduced cooler highboiling oil to arrest objectionable reaction prior to separation,following expansion, of vaporized components and residual components ofthese hot oil products, and in which the hot oil products from theheating operation prior to such cooling are passed in brief indirectheat exchanging relation with residual components separated from thecooled oil mixture to assist in cooling the hot oil products from theheating operation and to promote complete separation of low boilingcomponents from the residual oil mixture.

According to the present invention, a flowing stream of high boiling oilis heated to a high cracking temperature under superatmosphericpressure, the total stream of hot oil products from the heatingoperation is passed under maintained superatmospheric pressure inindirect heat exchanging relation with a body of residual oil in a vaporseparating receptacle, the pressure on the 115 stream of hot oilproducts from the heating operation is then reduced and they arereleased under reduced pressure within the vapor separating receptacle,a stream of cooler high boiling oil is introduced into the stream of hotoil products from the heating operation before these hot oil productsare released within the vapor separating receptacle but after the heatexchange with the body of residual oil therein, vapors including vaporsof the desired low boiling oil are taken off the heat exchange with thebody of residual oil therein, and residual oil is discharged from thevapor separating receptacle. The vapors taken off from the vaporseparating receptacle may be subjected to any suitable condensing orfractionating and condensing or other recovery operation.

The invention will be further described in connection with theaccompanying drawing which 5 illustrates, diagrammatically andconventionally,

fromthe vapor separating receptacle but afterin elevation and partly insection and with parts broken away, one form of apparatus adapted forcarrying out the invention.

In carrying out the invention in the apparatus illustrated, high boilingoil, gas 011 for example, is forced, as a stream, through the heatingconduit l in the heating furnace 2, the heat exchange coil 3 and thepressure regulating and reducing valve 4, successively, into the vaporseparating receptacle 5 by means of pump 6; the high boiling oil isheated to a high cracking temperature, 900950 F. for example, undersuperatmospheric pressure, 300-600 pounds per square inch as dischargedfrom the heating conduit for example, maintained and regulated by meansof valve 4, in the heating conduit 1; the pressure on the stream of hotoil products discharged from the heating conduit is reduced at the valve4, to a pressure approximating atmospheric pressure but sufiicient tomaintain flow through the rest of the apparatus for example; relativelycool high boiling oil, gas oil, crude oil or reduced crude oil, or ahigh boiling oil fraction produced in the operation-for example, isintroduced into the stream of hot oil products passing from the heatexchange coil 3 to the vapor separating receptacle 5 through connection7; vapors, including vaporized components of the hot oil productsdischarged from the heating conduit and any vaporized components of theintroduced cooling oil, separate from residual oil in the vaporseparating receptacle 5 and escape through connection 9, to recoveryapparatus for the separation and condensation of the low boiling oilproduct, gasoline for example; and a body of this residual oil is 9maintained in the lower end of vapor separating receptacle 5 normallysubmerging the heat exchange coil 3 from which residual oil isdischarged through connection 10 as the operation proceeds. The coolinghigh boiling oil may be introduced into the stream of hot oil productsdischarged from the heating conduit either be fore or after thereduction of pressure thereon, although the latter scheme of operationis usually more advantageous, but this cooling high boiling oil isintroduced into the hot oil products discharged from the heating conduitafter they have passed through the heat exchange coil 3 and before theyare released within the vapor separating receptacle 5. The rate ofintroduction of cooling high boiling oil may be regulated to make thetemperature of the resulting oil mixture so low that further reaction ofthe hot oil products discharged from the heating conduit 1 is arrested,although high enough to involve cracking 119 of components of theintroduced cooling oil, or

so low as to inhibit any cracking of any components of the resulting oilmixture; the temperature of the body of residual oil in the lower end 5of the vapor separating receptacle 5 may be maintainedjn the rangeapproximating 7008()0 F. or in a 'irange approximating GOO-700 F. forexample. The heat exchange coil 3 is advantageously arranged so that thepath of travel therethrough for the hot oil products discharged fromtheheating conduit is short to minimize the period of time over which thesehot oil products are subjected to cooling by. this indirect heatexchange. In the apparatus illustrated, the cooling high boiling oil isintroduced-through connection 7 in intimate mixture with the hot oilproducts discharged from the heating conduit. This cooling high boilingoil must be supplied through connection '7 at a temperature lower thanthat at which the hot oil products from the heating conduitenterconnection 8, but it may be used, beforelbeing :so supplied throughconnection '7, as a cooling medium in heat recovery heatexchangerslandso preheated to temperatures as high as 600 F. or higherprior to introduction into the, hot oil products discharged from theheating conduit.

' In initiating operation in the apparatus illus trated, high boilingoil is circulated from the 30 vapor separating receptacle 5 through theheat.- ing conduit 1 back to the vapor separating receptacle 5 by meansof pump 6 and connection 11, valve 12 in connection 11, however, beingclosed during normal operation. During normal opera- 35' tion, residualoil discharged from the vapor separating receptacle 5 through connectionis discharged through cooler 13 and connection 14.

The vapors escaping from the upper end of the vapor separatingreceptacle 5 through connection 9 are discharged into the lower end offractionating tower 15. This fractionating tower may, for example, be ofconventional bubble tower construction. The vapors remaining uncondensedescape from the upper end of fractionating tower 15 through connection16 to condenser 17 arranged to discharge into the receiver 1 8,ijioinwhich condensate is discharged through connection 19 and uncondensedvapors and gases through "connection 20. The operation of thefractionating tower may be controlled, or in part controlled, by theregulated introduction of a part of the condensate collected in receiver18, or. some similar low boiling fraction, into the upper endof thetower through connection 21 by means of pump 22. The operation of thefractionating tower 15 may also be controlled, in part, by the regulatedintroduction of raw hig'hboiling oil into the tower at an intermediatepoint through connection 23 by means of pump 24; .The operation of thefractionating tower 15 may also be controlled by regulated circulationof relatively cool high boiling oil through the heat exchange coil 25 bymeans of pump 26. An intermediate fraction may be discharged as acondensate from the fractionating tower 15 at an intermediate pointthrough connection 27. The apparatusillustrated is arranged to providefor return 'to the fractionating tower 15 of vapors entrained in suchdischarged condensate or separated therefrom by the maintenance of asomewhat lower pressure in the separator 28 than prevails in thefractionating tower 15 at the point irompwhic'h the condensate isdischarged, from 7 separator 28 through connection 29. Any intermediatefraction. so discharged is discharged from -oil supplied to the heatingconduit 1 by means or pump 6 may consist exclusively of a condensatefraction separated in the fractionating tower 15 or of raw oil suppliedthrough connection 32, or it may comprise a mixture including such acondensate fraction and raw oil.

The cooling high boiling oil supplied through connection 7 may consisteither of raw high boiling oil, such as crude oil or reduced crude oil,supplied through heat exchange coil 25 and connection 38, or of raw highboiling oil, such as gas oil or crude oil or reduced crude oil, suppliedthrough connections 36, 3'7 and 3 9, or of a condensate fractionsupplied from the lower end of fractionating towerv 15 through cooler 35and connections 37 and 39, or of any mixture of such oils or oilfractions.

I, The'coolers 13, 35 and 30, or such of these coolers as are utilizedin carrying out the invention in apparatus such as that illustrated, mayconsist of heat exchangers in which oil tobe processed or undergoingprocessing in the operation of the present invention or in some otheroperation is used as a cooling medium, or some extraneous coolingmedium, water for example, may be used as a cooling medium in thesecoolers. fl t) In the apparatus illustrated, the vapor separatingreceptacle 5, the iractionating tower 15, and connections '7, 8, 9, 33,34. and 38 are with advantage thoroughly lagged or thermally insulated.

In the improved method of operation provided by the present invention,any tendency toward entrainment of low boiling, or intermediate boiling,components, entrained or dissolved, in the residual oil discharged fromthe vapor separating receptacle is reduced to a minimum, although thisresidual oil includes not only very high boiling components of the hotoil products discharged from the heating'operation but also any veryhigh boiling components of the cooling high fig); boiling oil introducedinto thesehot oil products discharged from the heating operation, bymeans of a heat exchange which assists in cooling, or in initiating thecooling, of the hot oil products discharged from the heating operationbut which 1730 heat exchange, limited by the temperature differentialbetween the twomediainvolved as well as by the brief periodor" heatexchange preceding immediate further cooling of the hot oil products bydirect heat exchange with the introduced cooling oil, need not involveany objectionable further reaction of the hot oil productsdischargedfrom the heating operation. Any tendency toward deposition of carbon orpitch from thehot oil products discharged from the heating opera-. tionduring this heat exchange, in the heat ex-v change coil 3 in theapparatus illustrated, is minimized in the improved operation of thepresent invention by maintaining pressure on these hot oil productsthrough this heat exchange.

At the end of a run, the heating conduit 1 is pumped out and steamed outby means of connec tion 40. 7

We claim: 7

11 Inthe manufacture-of lowerboilinghydrocarbon oils from higher boilinghydrocarbon oils, the improvement which comprises heating a flowingstream of high boiling oil to'a high cracking temperature in excess ofapproximately900 F. under superatmospheric pressure and producing a highyield of gasoline. in a single passage through the heatiif 'g'joperation, passing the total stream of hot oil products from saidheating operation under maintained superatmospheric pressure in indirecth'iitexchanging relation with a body of residual oil in a vaporseparating recepta cle and thereby transferring a substantial quantityof heat from the "stream of hot oil products to the body of oil in thevapor separating receptacle and promoting a more complete separation oflow boiling components from the residual oil mixture, thereaftermaterially reducing: the pressure on said stream 01 11013 0. productsand releasing them under materially reduced pressure 'within said vaporseparating receptacle, introducing a stream of cooler high boiling oilinto said stream of hot oil products from said-heating operation beforethey are released within said vapor separating receptacle and aftersaidheat exchange with the body of r idual oil therein in sufficientquantity to arre {cracking of the hot oil products discharged om saidheating operation, and taking off vaporsgi ncluding vapors of thedesired low boiling oil from said vapor separating recarbon oils fromhigher boiling hydrocarbon oils,

the improvement which comprises heating a flowing stream of high boilingoil to a high cracking temperature in excess of approximately 900 F.under superatmospheric pressure and producing a high yield of gasolinein a single passage through the heating operation, passing the totalstream of hot oil products from said heating operation under maintainedsuperatmospheric pressure in indirect heat exchanging relation with abody of residual oil in a vapor separating receptacle and therebyvaporizing from said body of residual oil substantially all of the oilcomponents boiling below about 600 F., thereafter reducing the pressureon said stream of hot oil products and releasing them under reducedpressure within said vapor separating receptacle, introducing a streamof cooler high boiling oil into said stream of hot oil products fromsaid heating operation before they are released within said vaporseparating receptacle and after said heat exchange with the body ofresidual oil therein, and taking off vapors including vapors of thedesired low boiling oil from said vapor separating receptacle anddischarging residual oil therefrom.

EDWARD W. ISOM. EUGENE C. HERTHEL.

